Changes in population abundance, reproduction and habitat use of the rice-field rat, Rattus argentiventer, in relation to rice-crop growth stage in a lowland rice agroecosystem in Vietnam

Abstract

Context Rice-field rodent pests cause substantial economic losses in Asia. In Vietnam, the rice-field rat (Rattus argentiventer) causes 5–10% annual pre-harvest loss in rice yield. A sound ecological knowledge of this species would be useful for developing strategies for managing this pest. Aims We tested the hypotheses that there would be changes in the population abundance, breeding performance and habitat use of R. argentiventer in response to rice-crop growth stage. Methods Capture–mark–recapture and kill trapping and spool-and-line tracking were used to assess population abundance, breeding and habitat use in different rice-bank habitats, at 3–5-week intervals, through a 2-month flooding period and a rice cropping season. The study was conducted between October 2008 and April 2009 in An Giang Province in The Mekong Delta, Vietnam. Key results The population abundance of R. argentiventer was significantly related to rice-crop growth stage and rice-bank habitat. More rats were captured after harvest (P < 0.001) and more were captured in the large and medium-sized banks (P < 0.05). The breeding performance of adult females responded to rice-crop growth stage (P = 0.006). When rice cover was sparse, adult females were located in the burrows during the day, whereas when the cover became abundant, adult females remained in the fields during both the day and at night time. After harvest, rats returned to utilise burrows along rice-field banks. Conclusions and implications (1) Rat control activities should be conducted prior to the seedling stage of the rice crop, before the onset of breeding and when vegetative cover is sparse, allowing the animals to be targeted in their burrows; and (2) vegetation on the rice-field banks should be cut to <10 cm to limit the availability of suitable nesting habitat in large and medium-sized banks.